Some Epics are missing while selecting an Epic to add on a story

Issue Summary

When the next-gen project has an elevated amount of Epics three issues happen:

• Epics are not listed while adding a link on an issue
• On Backlog, some issues with Epic link won't display the Epic label on the card
• Boards grouped by Epics won't display all issues

Environment

• Jira Software Cloud
• Next-gen project with the Roadmap feature

Steps to Reproduce

1. Create a plan with several Epics (tests performed with 100)
2. Add issues to different Epics
   • Open an issue > click on the ... button > click on Add to Epic > search for random Epic
     • Some Epics won't be listed
   • Open the backlog, some issues will show the linked Epic label while on some issues the label will be missing
   • Group the board by Epic, some issues with an Epic will be missing

Expected Results

• Issues will show the Epic label on Backlog
• All Epics will be listed on the dropdown while adding issues to Epic
• All issues are listed on board whether they have an Epic link or not

Actual Results

• Issues don't have the Epic label on Backlog
• On the dropdown where we select an Epic to be added to the issue, some Epics are not available
• Some issues won't be displayed on board when grouping by Epic

Notes

The 'Add to Epic' issue is intermittent, not occurring to specific Epics.

Workaround